Crop protection is essential for an ever-intensifying agriculture, with growing world population resulting in over 9 billion humans on earth by the year 2050. Increasing human health and environmental concerns (climate change) as well as steeply rising regulatory hurdles and expenses to bring novel active substances to the market are shifting innovation from synthetic towards biological plant protection agents. Microbial biofertilizers and biocontrol agents are promising alternatives to agrochemicals in sustainable agriculture; however, the lack of effective formulations is a major limitation for their successful application in the field.
We address this challenge and develop principally new and fully soil degradable biosolutions - microbial seed coatings and granules, microbial spray formulations, encapsulated plant extracts, and slow/controlled release coatings to name a few for large-scale plant cultures like maize and wheat. It is our expertise to identify the most effective technology, coat or encapsulate the active ingredient in a way that it is protected against adverse environmental conditions (heat, UV, moisture) and released at the right time at the point of action. We work with GRAS materials, especially with cellulose, starch, lignin and various gums and labscale machinery that is indicative for industrial processes (rotating drum, fluidized bed coater, granulator). Main research efforts are dedicated to non-sporulating gram negative bacteria and their formulation process to improve the overall performance and shelf life in dry state.
Formulation of gram-negative bacteria
The scientific challenge is to elucidate microbial responses to multiple factors including the properties of the used materials, the formulation process itself and the environmental conditions during processing and storage, and to estimate the driving factors that impact stability (viability, shelf life, metabolic activity), performance (germination, plant penetration) and function (release efficiency). Desiccation stress is a major issue which can be tackled with a combination of protective adjuvants but also with particular pre-treatment of the bacteria.
Stability of microbial formulations
In general, bacterial viability is reduced by at least one log CFU/mL after drying, reduction is even more dramatic (2-3 logs), if non-sporulating bacteria are employed. Besides selecting suitable materials with distinct properties, the formulation process itself and environmental conditions during coating and storage are critically important. In fact, stability of microbial formulations is influenced by multiple factors. Some of them have been previously studied with respect to microbial viability and shelf life, however, no systematic studies have been performed that take into account complex and multiple interactions between seed or plant leaf surface and rhizobial cell biology, and the physical and chemical properties of employed materials. When using foliar spray, formulation development also has to consider successful delivery to the plant surface (droplet impaction, adhesion, biofilm formation) and microbial stability after repeated drying and re-wetting cycles during the day. This can be estimated before field tests in a climate chamber at various temperatures and relative humidities.
Characterisation of formulations
Biological formulations consist of several components including sticker, humidifier, filler, protectant. They need to fulfill physical criteria, such as hot/cold stability, low abrasion, good rainfastness as well as biological criteria of which the effectiveness of the active ingredient and the shelf life of the formulated product are most important. We fully characterize the formulations and formulated products considering both physico-chemical as well as biological data to finally evaluate the efficacy in plant assays or in the field of those that fit best the set criteria.
